U.S. patent application number 11/075107 was filed with the patent office on 2005-10-13 for method and an apparatus to read a barcode.
This patent application is currently assigned to Sick AG. Invention is credited to Hafner, Carl Joseph, Reichenbach, Juergen, Schopflin, Uwe.
Application Number | 20050224581 11/075107 |
Document ID | / |
Family ID | 34895539 |
Filed Date | 2005-10-13 |
United States Patent
Application |
20050224581 |
Kind Code |
A1 |
Reichenbach, Juergen ; et
al. |
October 13, 2005 |
Method and an apparatus to read a barcode
Abstract
The invention relates to a method of reading a machine-readable
barcode including a pre-determined number of code elements, in
particular bars and spaces, with a respective picture being taken
by means of optical imaging of at least two adjacent and/or
mutually overlapping part sections of the bar code, with the
individual part sections each including a code element and the part
sections including in sum all the code elements of the barcode,
with the pictures being stored in a data store, and with the stored
pictures or parts thereof being put together for the reconstruction
of the information encoded by the barcode. The invention further
relates to a corresponding apparatus.
Inventors: |
Reichenbach, Juergen;
(Emmendingen, DE) ; Hafner, Carl Joseph; (Reute,
DE) ; Schopflin, Uwe; (Niederwinden, DE) |
Correspondence
Address: |
HARNESS, DICKEY & PIERCE, P.L.C.
P.O. BOX 828
BLOOMFIELD HILLS
MI
48303
US
|
Assignee: |
Sick AG
Waldkirch/Breisgau
DE
|
Family ID: |
34895539 |
Appl. No.: |
11/075107 |
Filed: |
March 8, 2005 |
Current U.S.
Class: |
235/462.12 |
Current CPC
Class: |
G06K 7/14 20130101; G06K
7/1465 20130101; G06K 7/1491 20130101 |
Class at
Publication: |
235/462.12 |
International
Class: |
G06K 005/04; G06K
007/10; G06K 009/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 8, 2004 |
DE |
10 2004 017 504.7 |
Claims
What is claimed is:
1. A method of reading a machine-readable barcode (1) including a
pre-determined number of code elements, in particular bars and
spaces, characterized in that a respective picture (7, 9, 11) is
taken by means of optical imaging of at least two adjacent and/or
mutually overlapping part sections (13, 15, 17) of the barcode (1),
with the individual part sections (13, 15, 17) each including at
least one code element and the part sections (13, 15, 17) including
in sum all code elements of the barcode (1); in that the pictures
(7, 9, 11) are stored in a data store; and in that the stored
pictures (7, 9, 11) or parts (25) thereof are put together for the
reconstruction of the information encoded by the barcode (1).
2. A method in accordance with claim 1, characterized in that the
pictures (7, 9, 11) are taken by means of a picture-taking
apparatus, preferably a camera, in particular a linear camera or a
matrix camera.
3. A method in accordance with claim 1, characterized in that the
pictures (7, 9, 11) are taken sequentially, in particular at a
constant image frequency.
4. A method in accordance with claim 2, characterized in that the
barcode (1) is in particular moved at a constant speed relative to
the picture-taking apparatus for the taking of the pictures (7, 9,
11).
5. A method in accordance with claim 3, characterized in that the
barcode (1) is in particular moved at a constant speed relative to
the picture-taking apparatus for the taking of the pictures (7, 9,
11).
6. A method in accordance with claim 5, characterized in that, on
the putting together of the pictures (7, 9, 11) or of the parts
(25) thereof, their mutual relative positions are calculated from
the image frequency of the shots and the speed of the barcode
(1).
7. A method in accordance with claim 1, characterized in that, on
the putting together of the pictures (7, 9, 11) or of the parts
(25) thereof, their mutual relative positions are determined by
correlation of coinciding picture contents of the pictures (7, 9,
11) or of the parts (25) thereof.
8. A method in accordance with claim 1, characterized in that, on
the putting together of the pictures (7, 9, 11) or of the parts
(25) thereof, their mutual relative positions are determined by a
comparison of the picture positions at least of start, stop and/or
center marks of the barcode (1).
9. A method in accordance with claim 1, characterized in that the
stored pictures (7, 9, 11) or the parts (25) thereof are put
together in a reconstruction buffer.
10. A method in accordance with claim 1, characterized in that
respective picture contents of the pictures (7, 9, 11) extending
along at least one line (23) are put together for the
reconstruction of the information encoded by the barcode (1).
11. A method in accordance with claim 1, characterized in that the
pictures (7, 9, 11) or the parts (25) thereof are stored and/or put
together in a color representation, a gray value representation or
a binary representation.
12. A method in accordance with claim 11, characterized in that the
pictures (7, 9, 11) or the parts (25) thereof available in a color
representation or in a gray value representation are converted into
a binary representation.
13. A method in accordance with claim 1, characterized in that
image contents of the pictures (7, 9, 11) extending along a line
(23) and present in a binary representation are encoded by running
length.
14. An apparatus for the reading of a machine-readable barcode (1)
including a pre-determined number of code elements, in particular
bars and spaces, characterized by a picture-taking apparatus for
the taking of pictures (7, 9, 11) by means of optical imaging of at
least two adjacent and/or mutually overlapping part sections (13,
15, 17) of the barcode (1), with the individual part sections (13,
15, 17) each including at least one code element and the part
sections (13, 15, 17) including in sum all code elements of the
barcode (1); a data store for the storage of the pictures (7, 9,
11); and a reconstruction unit for the putting together of the
stored pictures (7, 9, 11) or of parts (25) thereof for the
reconstruction of the information encoded by the barcode (1).
15. An apparatus in accordance with claim 14, characterized in that
the picture-taking apparatus is a camera, in particular a linear
camera or a matrix camera.
Description
[0001] The invention relates to a method of reading a
machine-readable barcode including a pre-determined number of code
elements, in particular bars and spaces. The invention further
relates to a corresponding apparatus.
[0002] Such methods and apparatuses for the machine reading of a
barcode printed, for example, on a package are generally known.
Generally, a barcode can be read using a contact pen or a laser
scanner. It is furthermore also known to read a barcode by means of
a matrix camera which, unlike scanners, has no moving parts, but
photo-sensitive CCD elements, with a picture of the barcode being
able to be generated by optical imaging.
[0003] It is, however, a disadvantage with such a matrix camera
that it has a limited image field. This has the consequence that
only those barcodes can be read by a matrix camera which completely
fit into the image field of the matrix camera. In contrast,
barcodes which project beyond the image field of the matrix camera
due to their size cannot be read completely and can thus not be
decoded. A conventional size of the image field of a matrix camera
amounts, for example, to 30 mm.times.40 mm.
[0004] It is the underlying object of the present invention to
develop a method and an apparatus of the initially named kind such
that a barcode exceeding the size of the image field of a matrix
camera can also be decoded by means of the matrix camera.
[0005] This object is satisfied in accordance with the invention,
starting from a method of the initially named kind, in that a
respective picture is taken by means of optical imaging of at least
two part sections of the barcode which are adjacent and/or overlap
one another, with the individual part sections each including at
least one code element and the part sections including in sum all
the code elements of the barcode; in that the pictures are stored
in a data store; and in that the stored pictures or parts thereof
are put together for the reconstruction of the information encoded
by the barcode.
[0006] The part of the object relating to the apparatus is
satisfied, starting from an apparatus of the initially named kind,
by a picture-taking apparatus for the taking of pictures by means
of optical imaging of at least two part sections of the barcode
which are adjacent and/or overlap one another, with the individual
part sections each including at least one code element and the part
sections including in sum all the code elements of the barcode, by
a data store for the storage of the pictures and a reconstruction
unit for the putting together of the stored pictures or parts
thereof for the reconstruction of the information encoded by the
barcode.
[0007] The invention is characterized in that the part sections of
the barcode to be read, in particular of a 1D or 2D barcode, are
detected by means of optical imaging, in particular
photographically and two-dimensionally, are stored as pictures and
the pictures are subsequently put together to form an image of the
barcode such that the information encoded by the barcode can be
restored from the image of the barcode. An image of the barcode is
also to be understood as every picture of the barcode which permits
a complete reconstruction of the information encoded by the
barcode. The image thus has to extend only over the whole running
length of the barcode, but not over its whole height.
[0008] The part sections of the barcode each include at least one
code element. In order for a code element to be enclosed by a part
section of the barcode, the code element does not have to be
completely arranged inside the part section. It is rather
sufficient for a section of the code element encompassing the width
of the code element to be arranged inside the part section of the
barcode. This in particular means that the code elements do not
have to be taken over their whole height for the reconstruction of
the encoded information. All part regions together include all code
elements of the barcode.
[0009] A major advantage of the invention consists of the fact that
barcodes can also be read by means of a matrix camera or the like
which were previously not able to be read completely, and thus were
also not able to be decoded, due to the limited image field of the
matrix camera. In particular the module width of the barcode to be
read, i.e. the width of the narrowest code element, can be
increased. Barcodes with a larger module width are less prone to
insufficiencies on the printing of the barcode and can therefore be
read with greater reliability.
[0010] In accordance with an advantageous embodiment of the
invention, the pictures are taken by means of a picture-taking
apparatus, preferably a camera, in particular a linear camera or a
matrix camera. With a camera, the reading distance can be set
particularly easily by adjusting the focal length of the lens. A
camera is furthermore characterized by a high sensitivity with
low-contrast barcodes. With a linear camera or a matrix camera, the
barcode to be read is imaged optically on a linear or matrix-shaped
arrangement of CCD sensors. The barcode can in particular also be
illuminated by one or more LEDs of the camera.
[0011] It is furthermore proposed in accordance with the invention
that the pictures are taken sequentially, in particular with a
constant image frequency. It can hereby in particular be avoided
that a plurality of picture-taking apparatuses are required for the
taking of the pictures. When only one picture-taking apparatus is
used, the apparatus for the reading of the barcode can be
manufactured particularly cost-favorably. Generally, however, a
plurality of picture-taking apparatuses can be used.
[0012] It is particularly advantageous for the barcode to be moved
relative to the picture-taking apparatus, in particular at a
constant speed, for the taking of the pictures. This is in
particular of advantage when the bar code moves through the image
field of the picture-taking apparatus in this process. Adjacent
and/or mutually overlapping part sections of the barcode can hereby
be taken in a particularly simple manner. The barcode can, for
example, be moved relative to the picture-taking apparatus by means
of a conveyor belt.
[0013] In accordance with a particularly preferred embodiment of
the invention, on the putting together of the pictures or of the
parts thereof, their mutual relative positions are calculated from
the image frequency of the shots and the speed of the barcode. With
a constant image frequency f and a constant speed v, the shift
.DELTA.s of the sequentially taken pictures can in particular be
calculated from the ratio of the speed v and the image frequency f:
.DELTA.s.varies.v/f.
[0014] Additionally or alternatively, on the putting together of
the pictures or of the parts thereof, their mutual relative
positions can be determined by correlation of coinciding picture
contents of the pictures or of the parts thereof. The image of the
barcode can be generated in this process by superimposing the
coinciding picture contents of the pictures or of the parts
thereof. A determination of the mutual relative positions of the
pictures or of the parts thereof by correlation of coinciding
picture contents is preferably carried out when the speed of the
barcode and/or the image frequency of the shots is only known
approximately.
[0015] Additionally or alternatively, on the putting together of
the pictures or of the parts thereof, their mutual relative
positions can be determined by a comparison of the picture
positions at least of start, stop and/or center marks of the
barcode. The putting together of the pictures or of the parts
thereof or the correlation of coinciding picture contents is,
however, not limited to the use of specific start, stop and/or
center marks of the barcode. On the putting together or on the
correlation, the actual code elements can also be made use of by
which the relevant information is actually encoded. These code
elements can be used alternatively or additionally to the specific
start, stop and/or center marks of the barcode on the putting
together or on the correlation. The pictures or the parts thereof
can be put together to form the image of the barcode by
superimposition of the picture positions of e.g. the start, stop
and/or center marks. The picture positions, e.g. the start, stop
and/or center marks, are preferably used for the determination of
the mutual relative positions of the pictures or of the parts
thereof when the speed of the barcode and/or the image frequency of
the shots is at least largely unknown.
[0016] In accordance with a further preferred embodiment of the
invention, the stored pictures or the parts thereof are put
together in a reconstruction buffer. The reconstruction buffer can
be made as a separate component or as part of the data store in
which the pictures of the part sections of the barcode are
stored.
[0017] Respective picture contents of the pictures extending along
at least one line are preferably put together for the
reconstruction of the information encoded by the barcode. A line
formed by image points of a picture in a row next to one another
can in particular be orientated perpendicular to the longitudinal
extent of the code elements imaged in the picture. Generally,
however, the line used for the reconstruction can have any desired
angle with respect to the code elements. If the barcodes are
applied to conveyed objects and are read during the conveying of
the objects, the line can extend parallel to the conveying
direction, and indeed independently of the orientation of the
barcode relative to the conveying direction, i.e. it is
deliberately accepted in this version that the barcode extends
obliquely to the conveying direction. Such a slanted positioning of
the code elements relative to the line used for the reconstruction
is, however, completely unproblematic for the invention. It is
hereby made possible that only parts of the stored pictures have to
be put together to be able to fully decode the information encoded
in the barcode so that in particular the reconstruction buffer
requires less storage space. Furthermore, conventional algorithms,
which are based, for example, on a scanning process of the barcode
along a line can be used for the reconstruction of the barcode.
[0018] The pictures or the parts thereof can be stored and/or put
together in a color representation, a gray value representation or
a binary representation. The pictures or the parts thereof
available in a color representation or in a gray value
representation can in particular be converted into a binary
representation. The required storage space and the computing time
requirements for the putting together of the pictures can hereby be
reduced. Pictures in a color representation or a gray value
representation can be present, for example, on the reading of 2D
barcodes, in particular stack codes or matrix codes.
[0019] Picture contents of the pictures extending along a line and
present in a binary representation can be encoded along the running
length for non-lossy data compression. On the putting together of
the pictures or of the parts thereof, data sequences of the
pictures encoded along the running length can in particular be
superimposed.
[0020] Further advantageous features of the invention are recited
in the dependent claims.
[0021] The invention will be explained in more detail in the
following with reference to an embodiment and to the drawings;
there are shown in them:
[0022] FIGS. 1a-1d a barcode which is moved through the image field
of a matrix camera;
[0023] FIGS. 2a-2c a single frame sequence of the barcode of FIG.
1, with the pictures having been taken at different points in
time;
[0024] FIG. 3 a put-together single-frame sequence of the pictures
of FIG. 2; and
[0025] FIGS. 4a-4c the single-frame sequence of FIG. 2, with the
picture contents of the pictures extending along the lines shown
being read.
[0026] FIG. 1 shows a 1D barcode 1 to be read which includes a
pre-determined number of code elements 31, 33 of different widths.
Both the linear bars 31 and the spaces 33 present between the bars
are called code elements 31, 33 in this process. The barcode 1,
which can be printed on a package, is moved, for example by means
of a conveyor belt (not shown), along a movement direction 3
through the image field 5 of a matrix camera (not shown). FIGS. 1a
to 1d show the barcode 1 at different points in time of its
movement which takes place at a constant speed v. The speed v can,
however, also generally be variable. In contrast to FIG. 1, the
barcode 1 can also be moved obliquely through the image field 5 of
the matrix camera as long as the widths of all code elements 31, 33
of the barcode 1 can be detected.
[0027] As can in particular be recognized with reference to FIG.
1b, the barcode 1 does not completely fit into the image field 5 of
the matrix camera due to its size, but rather its two ends 27, 29
project laterally beyond the image field 5 of the matrix camera. In
FIGS. 1a and 1c, the barcode 1 is arranged with a respective one of
its two ends 27, 29 inside the image field 5. In FIG. 1d, the
barcode 1 has already left the image field 5 again.
[0028] FIGS. 2a to 2c show three pictures 7, 9, 11 of part sections
of the barcode 1 which were taken by means of the matrix camera at
the points in time shown in FIGS. 1a to 1c. In FIG. 2a, the
fore-running end of the barcode 1, when considered in the movement
direction 3, and an image 13 of a front part section of the barcode
1 are detected. In FIG. 2b, an image 15 of a central part section
of the barcode 1 is detected. FIG. 2c shows the trailing end of the
barcode 1, when considered in the movement direction 3, with an
image 17 of a rear part section of the barcode 1 being detected.
Generally, however, only two or any number of images can also be
taken. The pictures 7, 9, 11 taken by means of the matrix camera
are stored in a data store.
[0029] In this process, for example, a bar 19 of the barcode 1
(FIG. 1) is associated both with the front part section and with
the middle part section of the barcode 1. Accordingly, images 19',
19" of the bar 19 are contained in the pictures 7, 9 (FIG. 2). A
bar 21 of the barcode 1 (FIG. 1), in contrast, is associated with
both the rear part section and the middle part section of the
barcode 1, so that images 21', 21" are contained in the pictures 9,
11 (FIG. 2).
[0030] As is shown in FIG. 3, for the reconstruction of the
information encoded by the barcode 1, the pictures 7, 9, 11 are put
together in a reconstruction buffer (not shown) by means of a
reconstruction unit (not shown), for example a microprocessor, to
form a complete image of the barcode 1, with the picture 9 or 11
being displaced with respect to the picture 7 or 9 respectively by
.DELTA.s.sub.1 or .DELTA.s.sub.2 in the x direction which
corresponds to the movement direction 3 of the barcode 1. In FIG.
3, the pictures 7, 9, 11 are only offset with respect to one
another in the y direction for reasons of illustration.
[0031] The mutual displacement .DELTA.s.sub.1 or .DELTA.s.sub.2 of
the sequentially taken pictures 7, 9, or 9, 11 can be calculated
with a constant and known speed v from the product of the speed v
of the barcode 1 and of the time span t between the two shots:
.DELTA.s.sub.i.varies.v.s- ub.i.times.t.sub.i. Alternatively or
additionally, the displacement .DELTA.s.sub.i can also be
determined by correlation of the images of those code elements 31,
33 which are imaged in both pictures 7, 9 or 9, 11. As a rule, a
plurality of code elements 31, 33 arranged in a row and in
particular including the code element 19 or 21 respectively are
required for such a correlation. However, coinciding picture
contents can also be correlated which represent the surroundings of
the barcode 1.
[0032] The correlation of coinciding picture contents of the
pictures 7, 9, 11 can in particular be used for the fine correction
of a mutual shift .DELTA.s.sub.i calculated, for example, from the
product of a speed v of the barcode 1 only known approximately and
a time span t between the two shots. Moreover, the shift
.DELTA.s.sub.i can also be determined by a comparison of the
picture positions of start, stop and/or center marks of the barcode
1. Generally, the superimposing operation on the putting together
of the pictures 7, 9, 11 can consist of the averaging of
corresponding pixels of the pictures 7, 9, 11.
[0033] In accordance with a further embodiment of the invention, as
will be explained in the following, unlike in FIG. 3, only parts of
the pictures 7, 9, 11 are put together to form an image of the
barcode 1.
[0034] In FIGS. 4a to 4c, the pictures 7, 9, 11 of FIGS. 2a to 2c
are shown. Picture contents, for example pixel sequences 25 of the
pictures 7, 9, 11, extending along one or more lines 23 are first
read for the reconstruction of the information encoded by the
barcode 1. The lines 23 each extend perpendicular to the
longitudinal extent of the code elements 31, 33 imaged in the
respective picture 7, 9, 11. Unlike in FIG. 4, the lines 23 can,
however, also extend at different heights through the pictures 7,
9, 11 and/or obliquely to the longitudinal extent of the imaged
code elements 31, 33.
[0035] If the pixel sequences 25 read along the lines 23 are
present in a color or gray value representation, they can be
converted into a binary representation. Pixel sequences 25 present
in a binary representation can be encoded by running length so that
in particular the individual widths of the code elements 31, 33 of
the barcode 1 are present as sequential numerical values.
[0036] For the reconstruction of the information encoded by the
barcode 1, pixel sequences 25 read along one or more lines 23 are
put together in the reconstruction buffer already explained above
to form an image of the barcode 1, with the encoded information
being able to be reconstructed from the image of the barcode 1. An
averaged image of the barcode 1 can be generated with the aid of a
plurality of lines 23.
[0037] The mutual shift of the pixel sequences 25 of the taken
pictures 7, 9, 11 read along the lines 23 can be calculated or
determined in analogy to the calculation or determination of the
mutual shift of the taken pictures 7, 9 or 9, 11.
[0038] In the method in accordance with the invention, individual
pictures 7, 9, 11 of the barcode 1 or parts 25 thereof, in
particular pixel sequences 25 arranged along a line 23, taken by
means of a matrix camera, are displaced with respect to one another
and superimposed on one another in correct phase so that the
barcode 1 can be fully decoded.
Reference Numeral List
[0039] 1 barcode
[0040] 3 movement direction
[0041] 5 image field
[0042] 7, 9, 11 picture
[0043] 13, 15, 17 part section
[0044] 19 bar
[0045] 19', 19" image of a bar
[0046] 21 bar
[0047] 21', 21" image of a bar
[0048] 23 line
[0049] 25 pixel sequence
[0050] 27, 29 end of the barcode
[0051] 31, 33 code element
* * * * *